1. Field of the Invention
The invention relates to the field of wrapping tape about an elongated structure such as an electrical conductor. More particularly the invention relates to the field of wrapping tape supplied by a package of tape which is traverse, universal or level wound. The invention relates to the field of methods and apparatus for wrapping a plurality of different tapes from one or more multiple tape supply packages about a conductor during a single pass of a conductor through a wrapping machine.
2. Description of the Prior Art
In the past a variety of different methods and machines have been used for the wrapping of tape material around a length of an electrical conductor or cable. One of the methods used is the wrapping of the conductor with a single tape supplied from a pad. A pad is flat roll of tape with each turn of tape thereon completely overlapping a prior turn. In wrapping the pad is revolved concentrically or eccentrically about the circumference of the conductor to be wrapped while the conductor is advanced along its longitudinal axis. This method although quite reliable is inherently limited in rate of production since the speed of rotating the pad flyer or winding head which carries the tape pad and winds the tape around the conductor is limited by the maximum speed which the pad can withstand as it is revolved around the conductor. Overlapping of each wrap of tape also effects the production rate. For example, if a fifty percent overlap of tape on the conductor is desired the conductor must be advanced at a slower speed as compared to that where a ten percent overlap is desired.
It is also known in the art to wrap tapes around a construction such as a conductor from two or more separate pads concentrically or eccentrically mounted on a common winding head. Thus, the different tapes are applied from a plurality of pads at a single station in a rotational manner with respect to the length of the conductor or cable being wrapped. This method results in the first of a plurality of different tapes being wrapped directly around the conductor, the second tape of the plurality being wrapped directly around the first tape, and so forth.
Still another method known in the art is to wrap one or more single tapes around a conductor or cable by the use of pads of single tapes mounted on a plurality of different winding heads disposed at different stations spaced along the line of travel of the conductor or cable being wrapped. This method enables more layers of tape to be applied during a single pass of the conductor through the plurality of winding heads.
Whether a winding head carries one or a plurality of pads, the pads of tape are subjected to high rotational speed in being revolved concentrically or eccentrically around the longitudinal axis of the cable. Accordingly, the tape pads must be capable of withstanding an appreciable level of centrifugal force during the wrapping operation without coming apart. If the tape being used is comparatively narrow and if wound in a completely overlapping manner, the pad is quite unstable and can easily fall apart from the core upon which it is wound. A pad having each layer of tape completely overlapping adjacent layers necessarily requires a large diameter pad for a large supply of tape. Due to the maximum diameter of a pad which a wrapping machine is cable of accepting, the time period of operation is severely limited by the length of tape which can be mounted on the winding head, thus limiting the length of conductor which can be wrapped before stopping the head to install new pads.
These problems have been reduced by winding the tape packages in a traverse, universal, or level wound manner, that is to say the turns of tape advance along the length of the package alternatively from one end to the other thereof. Thus as one end of the package is reached by the winding of the tape, the tape is wound toward the opposite end of the package. Traverse winding of the tape package enables an appreciable length of tape material to be furnished in a single package without having the excess diameter for the same length of tape material which would result if the tape was wound in a fully overlapping fashion into a pad. Also, a tape package which is traverse wound can better resist centrifugal and windage forces at high winding speeds.
U.S. Pat. No. 533,934, which issued on Feb. 12, 1895 discloses a traverse wound cop having a plurality of parallel threads wound in a traverse manner. This patent also discloses an apparatus for winding the cop which includes a feed mechanism and friction wheel for varying the rate of movement of the threads in the traverse direction as the diameter of the cop increases during winding.
U.S. Pat. No. 2,372,400, which issued on Mar. 27, 1945, discloses traverse winding of strands or yarns of fibres of silk, cotton or the like, wherein one turn of a plurality of adjacent strands is partially overlapping upon the previous turn of a plurality of adjacent strands in order to interlock the strands on the package.
Machines for wrapping electrical conductors with a plurality of tapes each from a different pad of tape are manufactured by Aimco Division of The Entwistle Company, Bigelow Street Hudson, Mass. 01749. This company manufactures a Concentric Pad Type Taping Machine in which a single flyer or winding head at a single taping station carries as many as four pads, each having a single tape, mounted concentrically with the axis of rotation of the winding head. Such a machine can wrap a conductor with a pair of tapes from one pair of pads in an overlapping relationship such as half lapped and a second pair of tapes from another pair of pads, again in an overlapping relationship such as half lapped.
The Aimco Division manufactures an Eccentric Pad Type Tape Machine having a winding head with a number of different pads mounted about the periphery of the head with each pad having a single tape. Such a machine can apply, by way of example, four different tapes, each from a different one of four separate pads.
Aimco Division also manufactures a Concentric Cop Type Tape Machine which wraps a single tape from a traverse or universal wound supply package having its core disposed about the axis of rotation of the winding head.